Facebook's Monday announcement of its "social inbox" plan drew a lot of criticism from skeptics. Here are three reasons why that skepticism is warranted for business users.

Facebook's widely anticipated announcement Monday might have come as a surprise to some. It didn't, after all, announce a new e-mail service as many people had speculated. Not really, anyway.

Facebook unveiled a "social inbox"—a space that will serve as a hub for all communications people use online or via mobile phones, ranging from text messages and chat messages to, yes, e-mail messages, too.

CEO Mark Zuckerberg said that this new feature, which will be rolling out to users gradually during the next several months, is intended to make communications more "seamless, informal, immediate, personal, simple, minimal and short."

Jeremiah Owyang, an analyst at Altimeter Group, says that while adoption of Facebook's take on unified communications will probably be slow, it is a growing trend.

"This is the future, so while we may not see immediate adoption, we will all eventually have social inboxes," he says. Owyang predicts that Microsoft and Salesforce will both follow Facebook and eventually roll their own social inboxes.

Following Facebook's announcement, the public reaction on Twitter was quite skeptical. That reaction seems to back up Owyang's assertion that adoption will be slow—many Facebook users are worried about sending and receiving messages through the site, given its record with privacy and security. Others are skeptical that a social inbox really will simplify communications.

While Facebook's "social inbox" is an interesting idea, perhaps with longer-term promise as Owyang asserts, we see three reasons why many of you will stay away for now.

1. You're already attached to an e-mail provider.

People are creatures of habit, and if you're a longtime Gmail user, for example, making the switch to Facebook's social inbox is unlikely. Zuckerberg prefaced today's announcement with an anecdote about how high school students don't use e-mail because it's "too slow."

Messages will be instant and focus on streamlining conversations. Owyang says these young users—the ones without an allegiance to an e-mail provider—will be the early adopters of Facebook's messages.

2. You prefer keeping your communications methods separate.

Facebook's intent with Messages, Owyang says, is a continuation of its quest to become your starting place for communications. The problem with that, many find, is that Facebook is a hub for friendships (and pseudo-friendships, and people you might not actually know)—and not necessarily for business. Concerns about mixing work correspondences with Facebook will keep many from adopting Messages.

In addition, since e-mails, texts and chat conversations are delivered to your inbox (which, according to Facebook's description, will have different folders for spam and e-mails like bank statements), users are worried about message glut—too many messages in too many places, which could get confusing.

Though Facebook's Zuckerberg promises that communications via Messages will be private and secure, the possibility of a breach, exposed e-mail contacts or conversations are enough to make Facebook skeptics reject the new feature.